Integrative Nuclear Signaling in Cell Development—A Role for FGF Receptor-1

FGF2 gene transfer restores hippocampal functions in mouse models of Alzheimer's disease and has therapeutic implications for neurocognitive disorders

The adult hippocampus plays a central role in memory formation, synaptic plasticity, and neurogenesis. The subgranular zone of the dentate gyrus contains neural progenitor cells with self-renewal and multilineage potency. Transgene expression of familial Alzheimer's disease-linked mutants of β-amyloid precursor protein (APP) and presenilin-1 leads to a significant inhibition of neurogenesis, which is potentially linked to age-dependent memory loss. To investigate the effect of neurogenesis on cognitive function in a relevant disease model, FGF2 gene is delivered bilaterally to the hippocampi of APP+presenilin-1 bigenic mice via an adenoassociated virus serotype 2/1 hybrid (AAV2/1-FGF2). Animals injected with AAV2/1-FGF2 at a pre- or postsymptomatic stage show significantly improved spatial learning in the radial arm water maze test. A neuropathological investigation demonstrates that AAV2/1-FGF2 injection enhances the number of doublecortin, BrdU/NeuN, and c-fos-positive cells in the dentate gyrus, and the clearance of fibrillar amyloid-β peptide (Aβ) in the hippocampus. AAV2/1-FGF2 injection also enhances long-term potentiation in another APP mouse model (J20) compared with control AAV2/1-GFP-injected littermates. An in vitro study confirmed the enhanced neurogenesis of mouse neural stem cells by direct AAV2/1-FGF2 infection in an Aβ oligomer-sensitive manner. Further, FGF2 enhances Aβ phagocytosis in primary cultured microglia, and reduces Aβ production from primary cultured neurons after AAV2/1-FGF2 infection. Thus, our data indicate that virus-mediated FGF2 gene delivery has potential as an alternative therapy of Alzheimer's disease and possibly other neurocognitive disorders.

A putative role for endogenous FGF-2 in FGF-1 mediated differentiation of human preadipocytes

The defining characteristic of obesity is increased adipose tissue (AT) mass following chronic positive energy supply. AT mass is determined by adipocyte number and size, which reflect proliferation and differentiation of preadipocytes and hypertrophy of pre-existing adipocytes. The molecular pathways governing AT expansion are incompletely defined. We previously reported that FGF-1 primes proliferating primary human preadipocytes (phPA), thereby increasing adipogenesis. Here we examined whether FGF-1's adipogenic actions were due to modulation of other FGFs. Treatment of phPA with FGF-1 reduced FGF-2 mRNA/protein by 80%. To examine a putative functional role we performed siRNA knockdown studies. Following FGF-2 knockdown preadipocyte proliferation was decreased and expression of adipogenic genes (PPARγ, G3PDH and adiponectin) was increased at day 1 of differentiation. These results suggest that changes in endogenous FGF-2 levels contribute to FGF-1's early adipogenic effects and highlight the complexity of the paracrine interplay between FGFs within human AT.

FGFR2 protein expression in breast cancer: nuclear localisation and correlation with patient genotype

BACKGROUND

Single Nucleotide Polymorphisms (SNPs) in intron 2 of the Fibroblast Growth Factor Receptor Type 2 (FGFR2) gene, including rs2981582, contribute to multifactorial breast cancer susceptibility. The high risk polymorphism haplotype in the FGFR2 gene has been associated with increased mRNA transcription and altered transcription factor binding but the effect on FGFR2 protein expression is unknown. 40 breast tumours were identified from individuals with known rs2981582 genotype. Tumour sections were stained for FGFR2 protein expression, and scored for nuclear and cytoplasmic staining in tumour and surrounding normal tissue.

FINDINGS

FGFR2 immunohistochemistry demonstrated variable nuclear staining in normal tissue and tumour tissue, as well as consistent cytoplasmic staining. We did not find an association between nuclear staining for FGFR2 and genotype, and there was no association between FGFR2 staining and estrogen or progestogen receptor status. There was an association between presence of nuclear staining for FGFR2 in normal tissue and presence of nuclear staining in the adjacent tumour (Fishers exact test, p = 0.002).

CONCLUSIONS

Variable nuclear staining for FGFR2 in breast cancer, but an absence of correlation with rs2981582 genotype suggests that the mechanism of action of polymorphisms at the FGFR2 locus may be more complex than a direct effect on mRNA expression levels in the final cancer. The effect may relate to FGFR2 function or localisation during breast development or tumourigenesis. Nuclear localisation of FGFR2 suggests an important additional role for this protein in breast development and breast cancer, in addition to its function as a classical cell surface receptor.

Nuclear trafficking of the epidermal growth factor receptor family membrane proteins

Multiple membrane-bound receptor tyrosine kinases (RTKs), such as the epidermal growth factor receptor (EGFR) and ErbB-2, have been reported to be localized in the nucleus, where emerging evidence suggests that they are involved in transcriptional regulation, cell proliferation, DNA repair and chemo- and radio-resistance. Recent studies have shown that endocytosis and endosomal sorting are involved in the nuclear transport of cell surface RTKs. However, the detailed mechanism by which the full-length receptors embedded in the endosomal membrane travel all the way from the cell surface to the early endosomes and pass through the nuclear pore complexes is unknown. This important area has been overlooked for decades, which has hindered progress in our understanding of nuclear RTKs' functions. Here, we discuss the putative mechanisms by which EGFR family RTKs are shuttled into the nucleus. Understanding the trafficking mechanisms as to how RTKs are transported from the cell surface to the nucleus will significantly contribute to understanding the functions of the nuclear RTKs.

Phosphorylation and the Cajal body: modification in search of function

The Cajal body (CB) is a subnuclear domain that contains proteins and factors involved in a diverse range of activities including ribonucleoprotein maturation, histone gene transcription and telomerase assembly. Among these activities, the CBs' role in small nuclear ribonucleoprotein (snRNP) biogenesis is best characterized. Although CBs are found in plants, flies and mammals, not all cell types contain CBs. Rather, CBs are most prominent in transcriptionally active cells, such as cancer and neuronal cells. Many CB components, including the CB marker protein coilin, are phosphorylated in humans. The functional consequence of phosphorylation on CB assembly, activity and disassembly is largely unknown. Also unknown are the signaling pathways, kinases and phosphatases that act upon proteins which localize in the CB. The goal of this review is to demonstrate the need for a concerted effort towards elucidating the functional consequence of phosphorylation on CB formation and activity.

A complex role for FGF-2 in self-renewal, survival, and adhesion of human embryonic stem cells

The transcription program that is responsible for the pluripotency of human ESCs (hESCs) is believed to be comaintained by exogenous fibroblast growth factor-2 (FGF-2), which activates FGF receptors (FGFRs) and stimulates the mitogen-activated protein kinase (MAPK) pathway. However, the same pathway is stimulated by insulin receptors, insulin-like growth factor 1 receptors, and epidermal growth factor receptors. This mechanism is further complicated by intracrine FGF signals. Thus, the molecular mechanisms by which FGF-2 promotes the undifferentiated growth of hESCs are unclear. Here we show that, in undifferentiated hESCs, exogenous FGF-2 stimulated the expression of stem cell genes while suppressing cell death and apoptosis genes. Inhibition of autocrine FGF signaling caused upregulation of differentiation-related genes and downregulation of stem cell genes. Thus, exogenous FGF-2 reinforced the pluripotency maintenance program of intracrine FGF-2 signaling. Consistent with this hypothesis, expression of endogenous FGF-2 decreased during hESC differentiation and FGF-2 knockdown-induced hESC differentiation. In addition, FGF-2 signaling via FGFR2 activated MAPK kinase/extracellular signal-regulated kinase and AKT kinases, protected hESC from stress-induced cell death, and increased hESC adhesion and cloning efficiency. This stimulation of self-renewal, cell survival, and adhesion by exogenous and endogenous FGF-2 may synergize to maintain the undifferentiated growth of hESCs. Stem Cells2009;27:1847–1857

FGF-2, TGFbeta-1, PDGF-A and respective receptors expression in pleomorphic adenoma myoepithelial cells: an in vivo and in vitro study

Myoepithelial cells have an important role in salivary gland tumor development, contributing to a low grade of aggressiveness of these tumors. Normal myoepithelial cells are known by their suppressor function presenting increased expression of extracellular matrix genes and protease inhibitors. The importance of stromal cells and growth factors during tumor initiation and progression has been highlighted by recent literature. Many tumors result from the alteration of paracrine growth factors pathways. Growth factors mediate a wide variety of biological processes such as development, tissue repair and tumorigenesis, and also contribute to cellular proliferation and transformation in neoplastic cells.

OBJECTIVES

This study evaluated the expression of fibroblast growth factor-2 (FGF-2), transforming growth factor beta-1 (TGFbeta-1), platelet-derived growth factor-A (PDGF-A) and their respective receptors (FGFR-1, FGFR-2, TGFbetaR-II and PDGFR-alpha) in myoepithelial cells from pleomorphic adenomas (PA) by in vivo and in vitro experiments.

MATERIAL AND METHODS

Serial sections were obtained from paraffin-embedded PA samples obtained from the school's files. Myoepithelial cells were obtained from explants of PA tumors provided by surgery from different donors. Immunohistochemistry, cell culture and immunofluorescence assays were used to evaluate growth factor expression.

RESULTS

The present findings demonstrated that myoepithelial cells from PA were mainly positive to FGF-2 and FGFR-1 by immunohistochemistry and immunofluorescence. PDGF-A and PDGFR-alpha had moderate expression by immunohistochemistry and presented punctated deposits throughout cytoplasm of myoepithelial cells. FGFR-2, TGFbeta-1 and TGFbetaR-II were negative in all samples.

CONCLUSIONS

These data suggested that FGF-2 compared to the other studied growth factors has an important role in PA benign myoepithelial cells, probably contributing to proliferation of these cells through the FGFR-1.

Trafficking and cell migration

The migration of single cells and epithelial sheets is of great importance for gastrulation and organ formation in developing embryos and, if misregulated, can have dire consequences e.g. during cancer metastasis. A keystone of cell migration is the regulation of adhesive contacts, which are dynamically assembled and disassembled via endocytosis. Here, we discuss some of the basic concepts about the function of endocytic trafficking during cell migration: transport of integrins from the cell rear to the leading edge in fibroblasts; confinement of signalling to the front of single cells by endocytic transport of growth factors; regulation of movement coherence in multicellular sheets by cadherin turnover; and shaping of extracellular chemokine gradients. Taken together, endocytosis enables migrating cells and tissues to dynamically modulate their adhesion and signalling, allowing them to efficiently migrate through their extracellular environment.

Serotonergic hyperinnervation and effective serotonin blockade in an FGF receptor developmental model of psychosis

The role of fibroblast growth factor receptors (FGFR) in normal brain development has been well-documented in transgenic and knock-out mouse models. Changes in FGF and its receptors have also been observed in schizophrenia and related developmental disorders. The current study examines a transgenic th(tk-)/th(tk-) mouse model with FGF receptor signaling disruption targeted to dopamine (DA) neurons, resulting in neurodevelopmental, anatomical, and biochemical alterations similar to those observed in human schizophrenia. We show in th(tk-)/th(tk-) mice that hypoplastic development of DA systems induces serotonergic hyperinnervation of midbrain DA nuclei, demonstrating the co-developmental relationship between DA and 5-HT systems. Behaviorally, th(tk-)/th(tk-) mice displayed impaired sensory gaiting and reduced social interactions correctable by atypical antipsychotics (AAPD) and a specific 5-HT2A antagonist, M100907. The adult onset of neurochemical and behavioral deficits was consistent with the postpubertal time course of psychotic symptoms in schizophrenia and related disorders. The spectrum of abnormalities observed in th(tk-)/th(tk-) mice and the ability of AAPD to correct the behavioral deficits consistent with human psychosis suggests that midbrain 5-HT2A-controlling systems are important loci of therapeutic action. These results may provide further insight into the complex multi-neurotransmitter etiology of neurodevelopmental diseases such autism, bipolar disorder, Asperger's Syndrome and schizophrenia.

Fibroblast growth factor-2 regulates the stability of nuclear bodies

Nuclear bodies are distinct subnuclear structures. The survival of motoneuron (SMN) gene is mutated or deleted in patients with the neurodegenerative disease spinal muscular atrophy (SMA). The gene product SMN is a marker protein for one class of nuclear bodies denoted as nuclear gems. SMN has also been found in Cajal bodies, which co-localize with gems in many cell types. Interestingly, SMA patients display a reduced number of gems. Little is known about the regulation of nuclear body formation and stabilization. We have previously shown that a nuclear isoform of the fibroblast growth factor-2 (FGF-2(23)) binds directly to SMN. In this study, we analyzed the consequences of FGF-2(23) binding to SMN with regard to nuclear body formation. On a molecular level, we showed that FGF-2(23) competed with Gemin2 (a component of the SMN complex that is necessary for gem stabilization) for binding to SMN. Down-regulation of Gemin2 by siRNA caused destabilization of SMN-positive nuclear bodies. This process is reflected in both cellular and in vivo systems by a negative regulatory function of FGF-2 in nuclear body formation: in HEK293 cells, FGF-2(23) decreased the number of SMN-positive nuclear bodies. The same effect could be observed in motoneurons of FGF-2 transgenic mice. This study demonstrates the functional role of a growth factor in the regulation of structural entities of the nucleus.

Isolation and culture of fibroblasts from endoscopic duodenal biopsies of celiac patients

BACKGROUND

Fibroblasts are actually considered pivotal in inflammation and tissue remodelling process and for these reasons they are involved in the pathogenesis of autoimmune disorders such as celiac disease. Investigations to define the role of fibroblasts in celiac diseases are obstructed by the absence of specific models. Our objective is to isolate and culture primary fibroblasts from endoscopic duodenal biopsies of celiac and non-celiac subjects, to analyze their growth patterns and the morphometric characteristics.

METHODS

60 duodenal bioptic specimens from 20 celiac patients and 114 from 38 non-celiac subjects were mechanically chopped and enzymatically digested in order to obtain primary cell cultures. Growth patterns, karyotype (Q-banding analysis), expression of typing proteins (fibroblast surface protein and cytokeratin 20) and morphometric parameters (diameters and their ratio, perimeter, area and perimeter/area ratio at computerised image analysis) were investigated on cultured cells.

RESULTS

Primary cells were successfully cultured in 78% of the collected duodenal biopsies. Cultured cells, expressing the fibroblast surface protein, were negative for cytokeratine 20 and maintained a normal kariotype. Cells grew slowly without differences between the celiac and the non celiac group. Morphometric analysis of celiac fibroblasts revealed significantly increased dimensions, with a preserved diameters ratio, and a reduced perimeter/area ratio.

CONCLUSION

For the first time this study demonstrates the feasibility of culturing primary fibroblast cell from endoscopic duodenal biopsies in celiac and non-celiac subjects, opening a new window of opportunity in studies intended to establish the role of fibroblasts as a possible partaker in the pathogenesis of the celiac mucosal damage.

TC-5619: an alpha7 neuronal nicotinic receptor-selective agonist that demonstrates efficacy in animal models of the positive and negative symptoms and cognitive dysfunction of schizophrenia

A growing body of evidence suggests that the alpha7 neuronal nicotinic receptor (NNR) subtype is an important target for the development of novel therapies to treat schizophrenia, offering the possibility to address not only the positive but also the cognitive and negative symptoms associated with the disease. In order to probe the relationship of alpha7 function to relevant behavioral correlates we employed TC-5619, a novel selective agonist for the alpha7 NNR subtype. TC-5619 binds with very high affinity to the alpha7 subtype and is a potent full agonist. TC-5619 has little or no activity at other nicotinic receptors, including the alpha4beta2, ganglionic (alpha3beta4) and muscle subtypes. The transgenic th(tk-)/th(tk-) mouse model that reflects many of the developmental, anatomical, and multi-transmitter biochemical aspects of schizophrenia was used to assess the antipsychotic effects of TC-5619. In these mice TC-5619 acted both alone and synergistically with the antipsychotic clozapine to correct impaired pre-pulse inhibition (PPI) and social behavior which model positive and negative symptoms, respectively. Antipsychotic and cognitive effects of TC-5619 were also assessed in rats. Similar to the results in the transgenic mice, TC-5619 significantly reversed apomorphine-induced PPI deficits. In a novel object recognition paradigm in rats TC-5619 demonstrated long-lasting enhancement of memory over a wide dose range. These results suggest that alpha7-selective agonists such as TC-5619, either alone or in combination with antipsychotics, could offer a new approach to treating the constellation of symptoms associated with schizophrenia, including cognitive dysfunction.

Targeting novel integrative nuclear FGFR1 signaling by nanoparticle-mediated gene transfer stimulates neurogenesis in the adult brain

Neurogenesis, the process of differentiation of neuronal stem/progenitor cells (NS/PC) into mature neurons, holds the key to the treatment of various neurodegenerative disorders, which are a major health issue for the world's aging population. We report that targeting the novel integrative nuclear FGF Receptor 1 signaling (INFS) pathway enhances the latent potential of NS/PCs to undergo neuronal differentiation, thus promoting neurogenesis in the adult brain. Employing organically modified silica (ORMOSIL)-DNA nanoplexes to efficiently transfect recombinant nuclear forms of FGFR1 and its FGF-2 ligand into the brain subventricular zone, we find that INFS stimulates the NS/PC to withdraw from the cell cycle, differentiate into doublecortin expressing migratory neuroblasts and neurons that migrate to the olfactory bulb, subcortical brain regions and in the brain cortex. Thus, nanoparticle-mediated non-viral gene transfer may be used to induce selective differentiation of NS/PCs, providing a potentially significant impact on the treatment of a broad range of neurological disorders.

Fibroblast growth factor receptor-1 (FGFR1) nuclear dynamics reveal a novel mechanism in transcription control

Nuclear FGFR1 acts as a developmental gene regulator in cooperation with FGF-2, RSK1, and CREB-binding protein (CBP). FRAP analysis revealed three nuclear FGFR1 populations: i) a fast mobile, ii) a slower mobile population reflecting chromatin-bound FGFR1, and iii) an immobile FGFR1 population associated with the nuclear matrix. Factors (cAMP, CBP) that induce FGFR1-mediated gene activation shifted FGFR1 from the nuclear matrix (immobile) to chromatin (slow) and reduced the movement rate of the chromatin-bound population. Transcription inhibitors accelerated FGFR1 movement; the content of the chromatin-bound slow FGFR1 decreased, whereas the fast population increased. The transcriptional activation appears to involve conversion of the immobile matrix-bound and the fast nuclear FGFR1 into a slow chromatin-binding population through FGFR1's interaction with CBP, RSK1, and the high-molecular-weight form of FGF-2. Our findings support a general mechanism in which gene activation is governed by protein movement and collisions with other proteins and nuclear structures.

Chemokine receptor CCR2 undergoes transportin1-dependent nuclear translocation

Chemokines (CCs) are small chemoattractant cytokines involved in a wide variety of biological and pathological processes. Released by cells in the milieu, and extracellular matrix and activating signalling cascades upon binding to specific G protein-coupled receptors (GPCRs), they trigger many cellular events. In various pathologies, CCs are directly responsible for excessive recruitment of leukocytes to inflammatory sites and recent studies using chemokine receptor (CCR) antagonists permitted these molecules to reach the market for medical use. While interaction of CCs with their receptors has been extensively documented, downstream GPCR signalling cascades triggered by CC are less well understood. Given the pivotal role of chemokine receptor 2 (CCR2) in monocyte recruitment, activation and differentiation and its implication in several autoimmune-inflammatory pathologies, we searched for potential new CCR2-interacting proteins by engineering a modified CCR2 that we used as bait. Herein, we show the direct interaction of CCR2 with transportin1 (TRN1), which we demonstrate is followed by CCR2 receptor internalization. Further characterization of this novel interaction revealed that TRN1-binding to CCR2 increased upon time in agonist treated cells and promotes its nuclear translocation in a TRN1-dependent manner. Finally, we provide evidence that following translocation, the receptor localizes at the outer edge of the nuclear envelope where it is finally released from TRN1.

Immunohistochemical expression of basic fibroblast growth factor and fibroblast growth factor receptors 1 and 2 in the pathogenesis of lung cancer

PURPOSE

To identify the patterns of protein expression of basic fibroblast growth factor (bFGF) and FGF receptors 1 and 2 in non-small cell lung carcinoma (NSCLC) and their role in the early pathogenesis of squamous cell carcinoma (SCC) of the lung.

EXPERIMENTAL DESIGN

Archived tissue from NSCLC (adenocarcinoma and SCC; n = 321) and adjacent bronchial epithelial specimens (n = 426) were analyzed for the immunohistochemical expression of bFGF, FGFR1, and FGFR2, and the findings were correlated with clinicopathologic features of the patients.

RESULTS

High expression of bFGF, FGFR1, and FGFR2 was shown in most NSCLC tumors. The pattern of expression for all markers varied according to tumor histologic type and cellular localization. Cytoplasmic expression scores were significantly higher in tumors than in normal epithelia. Nuclear bFGF (P = 0.03) and FGFR1 (P = 0.02) levels were significantly higher in women than in men. Although cytoplasmic FGFR1 expression was significantly higher (P = 0.002) in ever smokers than in never smokers, nuclear FGFR1 (P = 0.0001) and FGFR2 (P = 0.003) expression was significantly higher in never smokers. Different prognostic patterns for the expression of these markers were detected for both NSCLC histologic types. Dysplastic changes showed significantly higher expression of all markers compared with squamous metaplasia.

CONCLUSIONS

bFGF, FGFR1, and FGFR2 are frequently overexpressed in SCC and adenocarcinoma of the lung. bFGF signaling pathway activation may be an early phenomenon in the pathogenesis of SCC and thus an attractive novel target for lung cancer chemopreventive and therapeutic strategies.